Metallurgists continually seek to exploit from available resources, such as elements in the periodic table of elements, different materials with favorable characteristics. Strength and weight are often competing design requirements that test the limits of known materials. In the design of aircraft and rockets, for example, there is a need for the continued development of high strength materials with low weights. When components are exposed to the high temperatures of rocket exhaust, there is a further need for materials with desirable physical properties that can also withstand very high temperatures and pressures.
One particularly useful metal is elemental rhenium. Rhenium has atomic number 75 in the periodic table of elements. It is known as a refractory metal meaning it has a high melting point. Rhenium metal melts at approximately 5756° F. However, rhenium begins to oxidize at a much lower temperature, approximately 1000° F. Rhenium retains excellent high temperature strength of approximately 6-9 Ksi (kips per square inch, 1000 pounds per square inch) at 4000° F. However, much before it reaches this temperature, the oxidation temperature of rhenium becomes a factor. The oxidation of rhenium produces a volatile oxide. Rhenium oxides will continually evaporate from the surface of the rhenium, even until the material is entirely vaporized.
Pure rhenium also has useful characteristics for fabrication of component parts. Rhenium has a high level of plastic deformation capability at low temperatures. This is an important quality of a reliable structural material. Rhenium metal is unique in this way compared to other high melting point metals which exhibit no plastic behavior when at lower temperatures. Rhenium's ductile behavior, however, is markedly degraded at very high temperature ranges. While at high temperatures, rhenium still has remarkable strength, its increasing brittleness becomes an issue. The high temperature brittle behavior of rhenium makes the mechanical limits of a component dependant on flaws and therefore not reproducible under all circumstances of design. A high temperature ductile version of pure rhenium would be desirable for structural use.
The above noted advantages of rhenium have made it a desirable material for use in rocketry applications. Rockets, missiles, and other vehicles that travel through and outside the earth's atmosphere can experience severe operating conditions including temperature and pressure extremes. Certain vehicle parts, including for example, valve bodies, nozzles, poppets, and seats, which are often located on the vehicle's propulsion or attitude control systems, can be subject to hot gas effluent. These components are directly exposed to high temperatures and pressures associated with hot gas effluent. Thus, there is an ongoing need to fabricate valves and nozzles from materials with improved strength and high temperature ductility.
Hence there is a need for an improved rhenium alloy. There is a need for a rhenium alloy with improved ductile properties at high temperatures compared to pure rhenium. Further the rhenium alloy should retain desirable characteristics of rhenium such as good high temperature strength and low temperature ductility. The improved rhenium alloy should be adaptable to the fabrication of rocket control components such as valves, valve bodies, poppets, seats, and nozzles. The present invention addresses one or more of these needs.